1. Field of the Invention
This invention relates to improvements in monopolar batteries, and more particularly to an improved positive feedthru terminal seal for lithium / metal sulfide cell assemblies.
2. Description of the Prior Art
Typical cell designs use heavy metal rings to compress a packing powder, typically boron nitride, to provide electrical isolation and sealing of the feedthru terminal. FIG. 1 illustrates such a prior art terminal feedthru seal 10 for positive terminal feedthru 12. The seal 10 includes a distributor plate 14 through which positive terminal feedthru 12 passes and which is maintained below the top cover of the battery cell. A pair of beryllia bushings 16 surround an insulating powder 18. A stainless steel seal body 20 encapsulates powder 18 between bushings 16. A stainless steel washer 22 and stainless steel external retaining ring 24 cap off the top of seal 10. Such a terminal feedthru assembly is relatively bulky and heavy.
There has been a recent need for new battery designs having size and weight restrictions. These restrictions limit cell designs to those having small cross sectional thicknesses and those having light weight. The use of heavy metal items 20, 22 and 24 will not work in the current cell configurations because of the weight and size restrictions imposed thereon. Accordingly, there is a need for an improved cell terminal feedthru.